1. Field of the Invention
The present invention relates to apparatus used in endodontia and has for an object a counter-angle head for carrying a drilling or filing tool or the like.
2. Description of the Prior Art
In the preparatory stages of conditioning the dental canals prior to filling them by medicinal means, the skilled artisan proceeds first to drilling operations. For effecting such operations, there have previously been proposed various instruments comprising particularly a counter-angle head equipped with a tool-carrying clamp and means for communicating to the tool-carrying clamp and thus the tool that it carries a back and forth motion beginning with a continuous, motor movement.
Counter-angle heads of the prior art comprise a cylindrical body provided with an axial bore in which is slidably mounted the slide of the tool-carrying clamp and also comprise a tubular body in which is mounted a rotary shaft terminating in an eccentric portion that cooperates in driving with the slide of the clamp. This eccentric portion is generally constituted by an element that extends toward the slide of the clamp parallel to the longitudinal axis of the rotary shaft and which is engaged in a notch provided in the slide of the clamp.
British Pat. No. 295,550 reaches an instrument of the type described above. According to this patent, the element is engaged in a cylindrical notch of the slide and the clamp is driven, relative to its longitudinal axis, into combined reciprocating movements, namely:
a reciprocating movement of translation the length of the axis,
and a reciprocating movement of rotation about the axis.
European Pat. No. 065,871 also teaches an instrument of the type described above, of which the eccentric element is engaged in a notch constituted by a groove extending parallel to the longitudinal axis of the slide. Consequently, the slide, the clamp and the tool are driven in a reciprocating rotary movement with respect to the longitudinal axis of the slide.
EP Pat. No. 0,161,196 also reaches an instrument, the eccentric member of which is engaged in a notch constituted by a groove of the slide effected along a plane perpendicular to the longitudinal axis such that the clamp and the tool are driven simultaneously in a reciprocating motion of axial translation.
The clamp of each of these instruments can be driven in only a single type of movement, which limits the applications of these instruments, whereas the usefulness of all three types of movement in the course of a single operation has been demonstrated. Moreover, the prior art instruments are not equipped with means permitting the automatic interruption of the movement of the tool when the forces applied to this latter are too great.